The distribution range of coastal plants with widespread marine seed dispersal across latitudes is often limited by their ecological adaptation to narrow temperature ranges. Such a narrow temperature range is a tradeoff between maintaining productivity at lower temperatures, and the ability to compete with more rapidly-growing species at higher temperatures. Kandelia candel and Kandelia obovata are sister mangrove species that display geographic divergence, with K. obovata being largely subtropical and K. candel being exclusively tropical. We leveraged on the parapatric distribution of these species to study the relationship between chilling tolerance and species distribution. Specifically, we compared the photochemical efficiency of photosystem II values of northern and southern populations of these species under chilling conditions. Kandelia obovata maintained significantly higher photochemical efficiency under chilling and more quickly recovered to pre-chilling levels than K. candel. Furthermore, the northern population of K. obovata maintained significantly higher photochemical efficiency than the southern population under chilling, while no intra-specific differences in chilling tolerance were found between K. candel populations. Hence, K. obovata is better adapted to the minimum temperatures encountered in the subtropics than K. candel, with populations at higher latitudes displaying higher chilling tolerance. These results underscore the importance of adaptation to different temperature brackets to the divergence of K. obovata and K. candel, and hint at the role of photosynthetic efficiency as a driving force behind the geographic divergence and speciation of coastal vegetation.

沿海植物在整个纬度上广泛分布的沿海种子的分布范围通常受到其对狭窄温度范围的生态适应的限制。如此窄的温度范围是在较低温度下保持生产率与在较高温度下与生长较快的物种竞争的能力之间的权衡。Kandelia candel和Kandelia obovata是显示地理差异的姊妹红树林物种，其中Oberta K.主要是亚热带的，而K. candel完全是热带。我们利用这些物种的父系分布研究耐寒性与物种分布之间的关系。具体来说，我们比较了这些物种在寒冷条件下北部和南部种群的光系统II值的光化学效率。低温下的Kandelia obovata与K. candel相比，光化学效率保持显着提高，并且恢复到预冷水平更快。此外，在寒冷条件下，北方种群的长叶隐孢子的光化学效率比南方种群高得多，而坎德氏梭菌之间的耐冷性没有种内差异。人口。因此，与宽叶K. candel相比，长叶K. obovata更适合亚热带地区遇到的最低温度，高纬度地区的种群显示出更高的耐寒性。这些结果强调了适应不同温度范围以适应长叶K. canova和K. candel差异的重要性，并暗示了光合作用效率是沿海植被地理差异和物种形成背后的驱动力。